The soil is changing.
Increasingly dry soils could spell big trouble for reservoirs, agriculture, forest health and pose greater risk of wildfire.
John Stulp was born on the Eastern Plains. Fifty years ago he began farming with his father-in-law near Lamar. Together he and his wife, Jane, brought up five children in southeastern Colorado, raising cattle and dryland wheat.
Along the way Stulp was elected as a Prowers County commissioner, and later served as Gov. Bill Ritter’s commissioner of agriculture and Gov. John Hickenlooper’s water policy adviser. When his service to the state was done in 2019, he headed back home to the prairie.
But the prairie is changing.
Winter wheat crops are becoming more unpredictable as hot, dry weather lasts longer. Where it once took 30 acres of pasture to support a cow and calf, it now takes 40 or more. As farming the prairie becomes a more marginal enterprise, ranchers are selling off cattle, farms are consolidating and families are leaving. Year after year, the area sets records: Driest summers. Driest winters. The last six months of 2021 were the hottest in Colorado’s recorded history, beating records set nearly a century ago in the Dust Bowl.
“We’re in trouble,” said Stulp, 73. Wheat planted in the fall in anticipation of being watered by winter snow is performing poorly, he said.
“The topsoil is so dried out, when we do get moisture, it doesn’t go very far. The wind sucks up the rest. It’s climate change, no question about it. If we get 3-4 degrees warmer like they say we might, it’ll look more like Albuquerque around here, and they don’t do a lot of farming around Albuquerque.”
Meanwhile, in Colorado’s high country, scientists monitoring snowpack in the mountains are noticing a strange phenomenon: even in strong snowpack years, it’s translating into less spring runoff into rivers and streams, as soils left parched by long stretches of hot weather drink first before any water runs on.
With Colorado facing a warmer future, scientists are looking at how increasingly dry soils could spell big trouble for reservoirs, agriculture, forest health and pose greater risk of wildfire.
“Even if precipitation doesn’t decline, a warmer future is a drier future,” said Peter Goble, a climatologist at Colorado State University’s Climate Center who studies soil moisture. “In a warmer world, the water we have gets used more quickly.”
The idea that dry soils soak up more snowpack isn’t new, Goble said, but the data is still emerging, and long-term trends are tough to suss out. Some soil moisture modeling data goes back to the 1970s in Colorado, but most consistent observations go back only to the 1990s. Scientists are still in the process of distributing networks of soil moisture monitors statewide.
As the body of data grows, the task ahead for climatologists is to gauge the accuracy of different soil moisture models developed by universities and weather monitoring agencies.
“Effectively predicting those spring streamflows is crucial to making the best use of the runoff we’re going to get,” Goble said.
Despite the limited data sets, scientists know soil aridity has been steadily increasing over the past 30 to 40 years, said Russ Schumacher, Colorado’s state climatologist.
“We’re still working on figuring out why,” he said. “Is it natural variability? Is it weather patterns? Or is it climate change? As best we can figure right now, about two-thirds of that aridity trend is tied to a warming climate.”
Scientists are also working to better understand the link between soil moisture and wildfire danger, Schumacher said. Dry soils can worsen the “vapor pressure deficit” — the ratio between the amount of water vapor in the air compared to how much the atmosphere could hold, a ratio that grows worse as temperatures rise.
Recent studies show a clear correlation between vapor pressure deficit and the intensity and size of wildfires, Schumacher said — and a strong link to climate change. Soil aridity can also seriously stress forest and grassland health, he said.
The past two springs saw runoff “underperform” in relation to snowpack, Schumacher said, owing to dry autumns that left soils like a wrung-out sponge.
Snowpack wasn’t terrible in Colorado last winter — the state’s river basins topped out in a range from 78% of the median in the southwestern corner of the state to 98% in the Upper Rio Grande basin, and 90% of the median in the South Platte drainage.
But the picture changed when an early, warm spring runoff season hit the Western Slope. What had been 89% of the median snowpack in the Yampa River basin in the state’s northwest corner translated into only 34% of normal streamflow, with the rest soaking into almost unquenchable soils.
The numbers were similar everywhere west of the Continental Divide. The Colorado River basin had 84% of median snowpack in March, but saw just 58% of normal streamflow. In the Gunnison basin, 80% of median snowpack turned into 48% of normal streamflow.
The impacts were wide-ranging. In the Sand Wash Basin in northwestern Colorado, Bureau of Land Management officials rounded up hundreds of wild horses as dry soil turned rangeland to “moon dust.”
Water managers issued a “call” on the Yampa River for the third time in history last summer, restricting how much junior water rights holders could draw from the river as it dwindled to a fraction of its normal flow. In southwestern Colorado, the Dolores River downstream of McPhee Reservoir dried up completely. In August, Blue Mesa Reservoir near Gunnison hit its second-lowest level since it was built as water managers sent tens of thousands of acre-feet downstream to prop up hydropower at an ailing Lake Powell.
Still, Colorado in 2021 avoided a repeat of the disastrous 2020 wildfire season that saw the three largest wildfires in state history, thanks in part to a robust summer monsoon season. Monsoon storms can help tamp down fire danger and alleviate soil aridity, but they do little for river flows because they’re short-term and localized, Schumacher said.
The situation on the Eastern Plains isn’t pretty, Schumacher said. Though spring 2021 brought healthy moisture to the prairie, “everything flipped in June.”
On the plains, winter snows do far less to recharge soil moisture than summer storms, Schumacher said.
“And last year, we just didn’t get the thunderstorms we expected,” he said.
Combined with months of record-breaking heat, the vapor pressure deficit skyrocketed, sucking water from the soil. The result can be devastating for livestock forage and farming.
Parts of far eastern Colorado got nearly two feet of snow in late January, though not enough to eliminate drought designations in the region.
What about 2022?
Colorado’s snowpack started 2022 in fairly decent shape with cautious optimism for spring runoff, according to the Colorado Basin River Forecast Center, a division of the National Oceanic and Atmospheric Administration.
Though 100% of Colorado remains in some level of drought, the mountains were hit with sometimes record-breaking snowfall in December. The strong monsoon season in the mountains last summer helped recharge dry soils — though much of far southwestern Colorado remains at no more than 30% of average soil moisture.
Snowpack was above 110% in several high Rockies river basins in early February, though the discrepancy between snowpack and soil moisture means it would likely take at least that much to translate into 100% of average streamflow. The Upper Rio Grande and Arkansas river basins lagged much of the state, sitting in the 90th percentile.
The center’s most recent water supply forecast, issued on Jan. 18, predicts inflow of 102% of normal into Blue Mesa Reservoir; 90% of average into McPhee Reservoir near Dolores; and 81% of normal into Navajo Reservoir straddling the Colorado-New Mexico border.
Currently, Blue Mesa Reservoir is below 30% full, according to the Western Colorado office of the Bureau of Reclamation, which oversees reservoirs. Despite the hopefully hefty spring runoff, Blue Mesa is unlikely to top 75% of its average capacity this summer.
Predicting the rest of the season is tricky, said Goble, the climatologist who studies soil moisture.
“It will be made or broken by one or two wet periods in the spring,” he said. “We’re still in a La Niña weather pattern, which can mean drier conditions. It’s a bit like playing poker with an ace and king out of the deck — you still might get a good hand, but you know from which cards are out which way the odds are tilted.”
The odds are likely to keep leaning that way, he said.
“As the West continues to warm, we expect snow to show up a little later and melt a little earlier,” he said. “Summer storms on the plains may not perform as well. There will be variation from year to year, but as things get warmer, we’re going to lose more water through evaporation.”
Stulp, who for decades has farmed the plains, said farmers and ranchers are doing their best to adapt. In the big picture, he said it’s time for farmers to figure out how to reduce carbon emissions. For now, though, no-till agriculture can help hold in moisture. GPS mapping can allow for more precise planting.
“But all the technology in the world doesn’t matter,” he said, “if you don’t get some help from Mother Nature.”
This story first appeared in Colorado Sunday, a premium magazine newsletter for members.
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